1 files changed, 74 insertions, 0 deletions
diff --git a/tests/src/asn1_helpers.c b/tests/src/asn1_helpers.c
new file mode 100644
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+++ b/tests/src/asn1_helpers.c
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+/** \file asn1_helpers.c
+ *
+ * \brief Helper functions for tests that manipulate ASN.1 data.
+ */
+
+/*
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+#include <test/helpers.h>
+#include <test/macros.h>
+
+#if defined(MBEDTLS_ASN1_PARSE_C)
+
+#include <mbedtls/asn1.h>
+
+int mbedtls_test_asn1_skip_integer( unsigned char **p, const unsigned char *end,
+                                    size_t min_bits, size_t max_bits,
+                                    int must_be_odd )
+{
+    size_t len;
+    size_t actual_bits;
+    unsigned char msb;
+    TEST_EQUAL( mbedtls_asn1_get_tag( p, end, &len,
+                                      MBEDTLS_ASN1_INTEGER ),
+                0 );
+
+    /* Check if the retrieved length doesn't extend the actual buffer's size.
+     * It is assumed here, that end >= p, which validates casting to size_t. */
+    TEST_ASSERT( len <= (size_t)( end - *p) );
+
+    /* Tolerate a slight departure from DER encoding:
+     * - 0 may be represented by an empty string or a 1-byte string.
+     * - The sign bit may be used as a value bit. */
+    if( ( len == 1 && ( *p )[0] == 0 ) ||
+        ( len > 1 && ( *p )[0] == 0 && ( ( *p )[1] & 0x80 ) != 0 ) )
+    {
+        ++( *p );
+        --len;
+    }
+    if( min_bits == 0 && len == 0 )
+        return( 1 );
+    msb = ( *p )[0];
+    TEST_ASSERT( msb != 0 );
+    actual_bits = 8 * ( len - 1 );
+    while( msb != 0 )
+    {
+        msb >>= 1;
+        ++actual_bits;
+    }
+    TEST_ASSERT( actual_bits >= min_bits );
+    TEST_ASSERT( actual_bits <= max_bits );
+    if( must_be_odd )
+        TEST_ASSERT( ( ( *p )[len-1] & 1 ) != 0 );
+    *p += len;
+    return( 1 );
+exit:
+    return( 0 );
+}
+
+#endif /* MBEDTLS_ASN1_PARSE_C */